Such a device is described in International patent application W094/09901. The reactor vessel is used there for treating oil, in particular for desulfurizing heavy oil by means of hydrogen gas, thereby forming hydrogen sulfide. To ensure that the highest hydrogen concentration prevails there where the highest per cent concentration of the most slowly convertible oil components is present, that is, at the end of the path to be followed by the oil, the oil and the hydrogen gas are passed through the channels in opposite directions.

In the International patent application mentioned, reference is made to a previously used desulfurization method in a different type of reactor vessel, in which the oil and the hydrogen gas were passed along a catalyst bed in the same direction. The use of the reactor vessel described in the International patent application mentioned, however, is limited to passing the substances entering into a reaction with each other through the vessel in opposite directions.

Accordingly, the first object of the invention is to make the reactor vessel suitable for reactions where the direction of flow of the substances entering into a reaction with each other is not of paramount importance.

In the reactor vessel, a variety of conventional physical processes can take place as well, such as those in which changes in gas-liquid equilibria of one or more components occur, for instance distillation processes, as well as adsorption/desorption processes of gases and liquids of different components and extraction processes of different liquids. The number of examples mentioned here, of course, is not limitative. Accordingly, carrying out a chemical reaction is not requisite in all cases. The term reactor vessel can be seen as a vessel in which both chemical processes and a variety of known physical processes take place.

A further object of the invention is to make the reactor vessel suitable for allowing a variety of chemical reactions to proceed selectively, in particular for delaying or suppressing, both serially and parallel, process steps in these reactions. Thus, the production of cyclohexanol starts from benzene, whereafter, upon a treatment with hydrogen gas in the above-mentioned known reactor vessel, cyclohexene is obtained, which, however, is directly converted further in the vessel to cyclohexane. The conversion of cyclohexene to cyclohexane is a less efficient reaction because for this purpose hydrogen is used, which upon a later oxidation of the cyclohexane to cyclohexanol is oxidized out again, yielding

water. This oxidation reaction moreover involves great hazards in view of the risk of explosion. It is therefore appealing to delay or suppress the conversion of cyclohexene to cyclohexane in the reactor vessel, such that the mixture coming from the reactor vessel contains a very high percentage of cyclohexene relative to the percentage of cyclohexane, if any is present therein. From M. Soede, Partial hydrogenation of aromatics (thesis 1996), Chapter IV, pp. 64/65, it is known that this can be achieved by reacting benzene under catalytic action in an aqueous environment.

Thereupon the cyclohexene reacts with water, whereby, depending on the reaction conditions, cyclohexanol can be formed directly, which, accordingly, occurs in an efficient and non-hazardous manner. In the last-mentioned publication, water in direct contact with the catalyst forms a diffusion barrier to the supplied benzene and the hydrogen gas. In such a situation, it can be said that a four-phase reaction system is involved, where a gas phase (hydrogen, optionally with benzene), a first liquid phase (benzene), a second liquid phase (water) and a solid phase (catalyst) are present. The known reactor vessel is based on a three-phase reaction system.

Accordingly, yet a further object of the invention is to make the reactor vessel suitable for a four-phase reaction system.

To meet the above objectives to a far-reaching extent, the reactor vessel such as it is described in the preamble is

characterized in that the buffer bodies are provided with a connection for a further liquid to be passed through the channels, which further liquid forms a diffusion barrier in the channels in the form of a liquid film on the channel wall, while the catalyst and the further liquid mentioned have a relatively high affinity for each other.

Insofar as the reactions proceeding in the reactor vessel are exothermic in nature, it is important that heat dissipation means be present therein. The inventors have appreciated that these heat dissipation means can be formed by the liquid film on the channel wall. The liquid to be supplied to the reactor vessel should therefore be such that it can form a liquid film on the catalyst surface, while this liquid, in addition to its function as diffusion barrier, is also suitable for heat removal.

In an advantageous embodiment of the reactor vessel, the connections for the polar liquid to be passed through the channels are connected with each other by means of a return pipe and a pump included therein, while, for the case where the liquid film is further to provide for the heat removal, a heat exchanger can be included in the return pipe.

The reactor vessel such as it is has been indicated hereinbefore is suitable in particular for catalytically reacting benzene and hydrogen gas, with water being used as diffusion barrier and for heat dissipation. Accordingly, the invention also relates to a method for the hydrogenating conversion of benzene into cyclohexene by reacting the

benzene with hydrogen gas under the influence of a catalyst, wherein, as a result of physical interaction, a water film is present on the surface of the catalyst as a diffusion barrier, and use is made of the reactor vessel indicated hereinbefore. In particular, further, the temperature and pressure in the reactor vessel can be such that the benzene is at least partly in the gas phase and the flow velocity of the water is so high relative to that of the benzene that the water film on the catalyst surface is maintained. The benzene in the gas phase exhibits turbulences at the interface with the water film flowing over the catalyst surface, which turbulences cause heat transfer to the water film to proceed more favorably.

The invention will now be further elucidated with reference to the accompanying drawings, wherein: Fig. 1 shows, in schematic representation, a longitudinal section of a reactor vessel according to the invention, while Fig. 2 shows a portion of a cross section.

The reactor vessel 1 with the catalyst elements 2 represented in Fig. 1 is described in detail in the International patent application W094/09901, the contents of which are to be considered inserted herein. The catalyst elements are formed by the channels 3. In Fig. 2 a cross section of three of these channels is represented. The channels 3 here have a circular form having in the longitudinal direction inwardly directed parts 4 between which extend grooves 5. The parts 4 and the grooves 5 have a

surface of a catalyst material 6, which is formed by a dispersion of Ruthenium, which may or may not be modified with one or more components, on a supporting material having a strong physical interaction with water. The support material may at the same time be the construction material of the channels of the reactor vessel or a covering layer to be provided on the wall of these channels. A detailed description of the catalyst composition is to be found in the above-mentioned publication"Partial hydrogenation of aromatics", Chapter I, pp. 13-15. In the above-mentioned International patent application, all kinds of possibilities for the design of the channels 3 are represented and described, so that this need not be discussed in more detail.

In the present design of the reactor vessel, it is built up from modules arranged vertically above each other, while the modules may or may not be separated by layers 7 of granular inert material or catalytic material, all as described with reference to Fig. 4 in the International patent application mentioned. Located at the top of the reactor vessel 1 is a buffer body 8 which is provided with connections 9,10 and 11 for the supply and mixing of substances entering into reaction with each other and a liquid forming a diffusion barrier. Similarly, at the lower end of the reactor vessel 1 there is a buffer body 12 which is provided with connections 13,14 and 15 for discharging and separating the reaction products and the liquid forming the diffusion barrier. For reasons of efficiency, the liquid forming the diffusion

barrier is recycled via a return pipe 16, in which a pump 17 is included, as well as a heat exchanger 18 for the case where the reaction taking place in the reactor vessel is exothermic in nature and heat is removed by utilizing the liquid film on the catalyst layer.

The reactor vessel described here with reference to the International patent application mentioned is suitable in particular for the preparation of cyclohexene through hydrogenation of benzene. As reporte in detail in the above publication"Partial hydrogenation of aromatics", the further conversion of cyclohexene to cyclohexane can then be suppressed virtually completely, or at least to a major extent, by having the hydrogenation proceed in an aqueous environment, viz. by having the water form a diffusion barrier between the substances entering into a reaction with each other, viz. benzene and hydrogen gas, and the catalyst layer. Via the buffer 8, hydrogen gas is supplied through the connection 9, benzene through the connection 10 and water through the connection 11. Because the water has a strong affinity for the catalyst material, it will flow along the inside surface of the channels 3 and so form a liquid film there. Insofar as the benzene is supplied in the liquid phase, it will flow through the grooves 5, while the hydrogen gas will flow through the central portion 19 of the reactor vessel. Hydrogen gas and benzene are passed through the reactor vessel in the same direction. The manner in which the reaction proceeds further has already been described in the

above-mentioned publication"Partial hydrogenation of aromatics". Via the buffer 12, after separation of the components in question, the remainder of hydrogen gas is discharged through the connection 13, the cyclohexene obtained, possibly in the presence of cyclohexane and unreacted benzene, is discharged through the connection 14, while the diffusion liquid is led through the connection 15 into the return pipe to be recycled. In view of the fact that the reaction mentioned here is exothermic in nature, heat is to be dissipated. This occurs by way of the liquid forming the diffusion barrier. A better control of the processes, including the heat and mass transfer, however, can be realized when the benzene is supplied partly or wholly in gaseous form. Of course, this causes a mixing with the hydrogen gas in the separate channels. Owing to the presence of the gas phase at the interface with the liquid film, the occurrence of turbulences yields a better heat transfer. When benzene is supplied in gaseous form and is active in that form in the reactor vessel, a temperature and pressure prevail in the vessel, such that water makes the transition to the vapor form. For that reason, to prevent the water diffusion layer on the inner wall of the channels being affected, the flow velocity of the water must be considerably higher than that of the benzene.

The invention is not limited to the embodiment described here with reference to the drawings and to the conversion of benzene to cyclohexene described by way of example here. All

kinds of modifications of the reactor vessel design as represented are possible, and so are many chemical reactions, based on a three-phase system, in which one of the phases is the liquid forming the diffusion barrier, or on a four-phase system for delaying or suppressing undesired products. Of course, these modifications and reactions are not to go beyond the scope of protection of the appended claims. In particular, it should be pointed out that the use of the reactor vessel can be such that, depending on the type of reaction, it is better in some cases for the substances entering into a reaction with each other to be passed through the vessel in the same direction and in other cases in mutually opposite directions.

Other examples of reactions that can take place in the reactor vessel are: -Homogeneous catalysis; here, use is made of a catalytic solution which, again, is retained by the inwardly directed parts 4 in the channels 3 in question. In the gas phase, and optionally an additional liquid phase which is not miscible with the catalytic solution, the substances entering into a reaction with each other are supplied. In. the catalytic liquid, the desired conversion takes place. The product formed is discharged either in the gas phase or by way of the additional liquid phase. The system can be operated both cocurrently and countercurrently.

-Polymerization; in polymerization, it is sometimes desired to make a polymer with a very small spread in degree

of polymerization. The catalyst is present again on or in the surface of the inwardly directed parts 4. Through the grooves 5 a viscous liquid flows down, in which viscous liquid optionally one of the reactants is supplied, while in the gas phase the reactants, or the other reactants, respectively, are supplied. The polymerization proceeds in the viscous solution at the interface with the catalyst. By varying the flow velocity of the gas or gases and the liquid or liquids separately, the degree of polymerization can be eminently controlled, both cocurrently and countercurrently.

-Reactive extraction; this involves an equilibrium- limited chemical conversion, such as, for instance, an esterification of an organic acid with an alcohol over an acid catalyst to form an ester. In this conversion, water is formed which is to be discharged to sustain the conversion to the ester to a maximum. Use is made of an acid catalyst which is provided on the inwardly directed parts 4, while the organic acid and the ester formed are led through the grooves 5. Via the central space in the channels, the alcohol is supplied and the water formed is discharged. The alcohol and the water can both be in the gas phase or both be in the liquid phase, while also the alcohol can be present in the liquid phase and water in the gas phase. The liquid in the grooves 5 will preferably flow top-down, while the gases and other liquids preferably move countercurrently thereto.